1. Field of the Invention
This invention relates to a drive control apparatus of automatic transmission device for use in automotive vehicles, and more particularly, to a stroke sensor and a position switch capable of controlling a fluid pressure actuator installed in an automatic transmission device for use in automotive vehicles in which the stroke sensor, when in an abnormal state is backed up by the position switch to hastily actuate the fluid pressure actuator.
2. Description of the Prior Art
A conventional drive control apparatus of an automatic transmission device for use in automotive vehicles is disclosed, for example, in Japanese Patent Application Early Laid-open Publication No. Sho 58-177725 and includes a fluid pressure actuator comprising two hydraulic cylinders for displacing a shift lever in a shift direction and a select direction which are at right angles to each other, and an electromagnetic operation type direction control valve for supplying and discharging a hydraulic oil to and from the actuator, the control valve being automatically controlled through a hydraulic control circuit.
Furthermore, there was recently proposed a device, as disclosed for example in Japanese Patent Application Early Laid-open Publication No. Sho 62-137450 and Japanese Utility Model Application No. Sho 62-63194, which includes a fluid pressure actuator comprising a hydraulic cylinder, an electromagnetic valve for controlling the activation of the cylinder, a control unit with a microcomputer built therein for controlling the activation of the electromagnetic valve, and a position switch (or a stroke sensor capable of continuously detecting the displacement of the actuator) for detecting the displacement of the actuator and inputting a signal thereof into the control unit. The best position of the actuator is thereby obtained by calculation based on the input information, such as a position of an accelerator pedal, the number of rotations of an engine, etc. of automobile, which is to be input into the control unit, and a control signal thereof is output into the electromagnetic valve to automatically and remotely control the activation of the actuator.
However, this conventional drive control device, if the stroke sensor should become inoperable because of, for example, a wire cut trouble or the like, the controlling by the control unit would not work, which is very risky for a running automobile.